MK4 Parts that fit MK3S+

These are the only MK4 R2 Parts unmodified* that will work with the MK3S+. These can be printed all on one plate. This list includes all parts for the Y axis, the new filament guide, and the heatbed cover.  Nothing else is compatible. These parts are in the same orientation as they are in the official Prusa g-code files.

Parts include:

• Y motor holder
• Y belt idler
• Y belt holder
• Y belt holder tensioner
• Y rod holder (4x)
• Heatbed cable cover top
• Heatbed cable cover bottom
• Filament guide

*Important Note!

I didnt want to alter the official part as that is the point of this whole listing, but unless you get the new MK4 bearing brackets and pads, you will need to place a cutting plane and slice off the top of the Y motor holder in Prusaslicer so the MK3S+ bed doesnt hit the top of it. Cut off off the few mm on the small part that is turned up at the end so none of the part protrudes past the top of the frame.  If you got the new MK4 bearing kit from the shop (which is not a printed part and has new rubber pads which raise the bed up a slight bit higher than the MK3s+, this slice shouldnt be needed to be done as roughly the same bed is used on the MK4.

Why no other printed parts?

The new MK4 Z axis parts wont work since they need 10mm rods. The  new MK4 X axis parts depends on these 10mm Z axis rod holes, their position, and larger bearing holes, so nothing on the X axis is compatible with the MK3S+.  The Nextruder is obviously completely different as is the LCD. 

The new LCD cable frame management ribbon clips are non printable parts, and the electronics box is metal. The spool holder is the same part you already have.

Other than an official upgrade path,  what non-printed parts might be used?

The first three parts below stand out to me as being particularly useful and possible:

• Update - I did this one - find full instructions here ! A new non-printed part on the MK4 that could be used on the MK3S+ is the new nylon strain relief cord for the heater cable bundle. You would need to drill a hole in your electronics enclosure to secure that end of it. See how this is done in the MK4 instructions - there is a separate hole just below the cable bundle on the electronics box for it. The length might need to be trimmed carefully (wearing goggles).  They dont sell this part in the store but I used a Ryobi 2.5mm thick weed wacker nylon piece of cord I had in the garage. It was orange too!  It worked perfectly and added much needed perfectly curved shape to the cable and also strain relief. I am using the new heater bed bracket here from the MK4 on my MK3S+. (Note the Einsy case back is a different mod I made that you can find here - I think it looks better in black than orange)

• The new non printed LCD ribbon frame clips could definitely be used, or if a printed part model was available this could be printed in the suggested material.
• The new MK4 Y bearing clips have a rubber pad in them and would be good to add if they are available, as well as positioning the bed at the right height for the new Y motor mount, so you dont need to cut the top off of it.
• Some caveats with this last one. If the MK3S+ board fits into the new metal electronics box, then you could print the two additional cable bracket parts that are available that allow you to attach the cables to that box.  The heater bed thermistor is the same part but I am not sure about the heat bed power cable. The bed textile sleeve is the same for the MK4 and MK3s+.

(From the Prusa print instructions:)

Print instructions

Download the latest PrusaSlicer and use the following settings**:

• Print settings: 0.20mm QUALITY
• Filament: PETG (tested on Prusament)
• 15% Grid infill

** Note that print settings are recommended, but you can experiment with your own.